Nest-Site Selection Patterns of Coexisting Sandhill and Whooping Cranes in Wisconsin

Abstract

Breeding sandhill cranes Antigone canadensis and released captive-reared whooping cranes Grus americana have coexisted in central Wisconsin since 2001. Despite 15 y of reintroduction efforts, the reproductive success of these whooping cranes has been near zero. Preliminary data suggest sandhill cranes nesting in central Wisconsin have apparent nest success rates that are similar to those reported from other populations in the region (~50%). One hypothesized cause of the whooping crane population's low reproductive success is nest abandonment induced by blood-feeding ornithophilic black flies Diptera: Simuliidae. Species-specific differences in selection of nest sites could influence the abundance of black flies at nests and affect reproductive success rates. We measured multiple vegetative and hydrologic characteristics at 35 sandhill crane nests, 20 whooping crane nests, and 164 randomly selected locations at 5-and 200-m scales. We were unable to detect a species-specific difference in vegetation characteristics within 5 m of nest sites. At the 200-m scale, sandhill cranes built nests at sites with slightly greater coverage of woody vegetation than whooping cranes. Differences observed between nest sites of sandhill and whooping cranes appeared to be slight and likely insufficient to explain the dramatic differences in reproductive success in central Wisconsin.Keywords: endangered; habitat; nest; reintroduced; sandhill crane; selection; whooping crane